An LCD has the advantages of portability, low power consumption, and low radiation, and has been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras and the like. Furthermore, the LCD is considered by many to have the potential to completely replace CRT (cathode ray tube) monitors and televisions. An LCD generally includes a liquid crystal panel, a driving circuit for driving the liquid crystal panel, and a backlight module for illuminating the liquid crystal panel.
FIG. 5 is essentially an abbreviated circuit diagram of a typical driving circuit 10 of an LCD. The driving circuit 10 includes a number n (where n is a natural number) of gate lines 101 that are parallel to each other and that each extend along a first direction, a number m (where m is also a natural number) of data lines 102 that are parallel to each other and that each extend along a second direction orthogonal to the first direction, a plurality of thin film transistors (TFTs) 103 that function as switching elements, a plurality of pixel electrodes 104, a gate driving circuit 110, and a data driving circuit 120. The crossed gate lines 101 and data lines 102 define an array of pixel units of the LCD. Each TFT 103 is provided in the vicinity of a respective point of intersection of the gate lines 101 and the data lines 102. The gate driving circuit 110 is used to drive the gate lines 101. The data driving circuit 120 is used to drive the data lines 102.
FIG. 6 is an equivalent circuit diagram relating to the driving circuit 10 at one of the pixel units. A gate electrode 1031, a source electrode 1032, and a drain electrode 1033 of the TFT 103 are connected to a corresponding gate line 101, a corresponding data line 102, and a corresponding pixel electrode 104 respectively. Cgd is a parasitic capacitor formed between the gate electrode 1031 and the drain electrode 1033 of the TFT 103.
The gate line 101 has an essential resistance R, which associated with the parasitic capacitor Cgd forms an RC (resistance-capacitance) delay circuit. The RC delay circuit distorts a scanning signal applied to the gate line 101. A distortion of the scanning signal is determined by the essential resistance R and a capacitance of the parasitic capacitor Cgd.
Referring also to FIG. 7, this is a waveform diagram showing distortion of a scanning signal applied to any one of the gate lines 101. Von represents a gate-on voltage of the TFT 103. Voff represents a gate-off voltage of the TFT 103. Vg1 shows a waveform of the scanning signal when the scanning signal is adjacent the gate driving circuit 110. Vg2 shows a waveform of the scanning signal when the scanning signal is far from the gate driving circuit 110. As seen, Vg2 is distorted, such that the switching on time of the corresponding TFT 103 is delayed for a period of “t” seconds.
Because the switching on time of the TFTs 103 far from the gate driving circuit 110 is delayed, these TFTs 103 are turned off when they should be turned on. At the same time, the data driving circuit 120 outputs data signals on time; thus the data signals are applied to the source electrodes 1032 of the TFTs 103 in a very short time. As a result, insufficient charging of the pixel units far from the gate driving circuit 110 and electrical leakage may occur. This in turn impairs the display quality of the LCD. For example, flickering of displayed images may occur.
What is needed, therefore, is a new driving circuit of an LCD that can overcome the above-described deficiencies. What is also needed is an LCD using such a driving circuit.